| 研究実績の概要 |
Over the last two years, we have significantly expanded our understanding of how the flow of a viscoelastic fluid past an object in a microchannel can destabilize due fluid elasticity. For flow past a single cylinder, an elastic instability causes the fluid to randomly choose one of the two paths past the cylinder. In FY2020, we performed a detailed numerical and experimental study using different fluids to show that a suitible combination of shear-thinning viscosity and fluid elasticity are required for the instability to occur. We also discovered that if two cylinders are situated in the channel side-by-side, regions of bistability and tristability can be observed where the fluid can randomly choose to pass through one, or two, of the three available paths.
In FY2021, we sought to further our understanding of how the size of the cylinder affects the flow instability. We carried out a detailed, systematic study by varying the size of the cylinder while keeping the channel width constant. A phase diagram illustrating the flow behaviour as a function of flow rate and cylinder size was constructed. For a large enough cylinder, we found a novel instability where vortices form upstream of the cylinder attached to the wall. A detour was taken from the phase diagram work to perform a detailed study of this new phenomena and a paper has been submitted on it to Soft Matter and is now undergoing revisions. The remaining phase diagram work is now in the paper preparation stage and will be submitted in a few months.
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